The upper and lower frames of a dental articulator normally include dental cast mounting plates to which are attached dental casts of a patient's upper and lower teeth or gums. In the attachment process, the casts are held in a desired predetermined position by suitable apparatus and they are then attached to the dental cast mounting plates on the articulator by soft plaster. After the plaster has hardened, the mounting apparatus is removed and the dental casts are then properly held by the plaster to the articulator frames, thus enabling the articulator frames to be hinged and manipulated in a desired manner to simulate jaw movements.
Dental cast mounting plates have been made in a variety of shapes and configurations. Mostly, they have been relatively flat plates with one or more upwardly extending projections to facilitate attachment to the plaster to the plate. The moist plaster typically has a consistency similar to that of whipped cream or shaving creams such that the plaster tends to stay somewhat where it is placed, but usually a certain amount of plaster flows or squeezes outwardly beyond the periphery of the dental cast and the mounting plate. Since the consistency of the plaster varies the amount of the wet plaster squeezed from beneath the plate and the cast varies. However, in almost all instances some clean-up is required to remove this excess material. Some of this clean-up can occur while the plaster is still soft, but the remainder must be completed by scraping and sanding after the material has hardened, which requires time as well as some skill and patience and may also damage the edges of the mounting plate.
In an attempt to alleviate this problem, some dental cast mounting plates include a short outer wall to confine the soft plaster. One example of this is shown in U.S. Pat. No. 4,600,385. While such wall is of assistance, in placing the soft plaster, it is more difficult to removed hardened plaster from the outer edges of plates having the fixed outer wall. Further, there are "split-cast" mounting plates as shown in this patent application, designed to be viewed from the side with a dental cast mounted thereon, so that the interface between the mounting p late and the cast can be observed to check the alignment and accuracy of the original mounting and cast replacement operation. A fixed outer wall on such mounting plates would interfere with this inter face viewing. Use of this "split-cast" type of plate therefore requires particular care in removal of excess plaster to facilitate such observations. Also, there is danger of damaging such a plate while scraping or sanding away the hardened plaster. This damage or change in the plate surfaces also creates inaccuracies in reuse.
Accordingly a need exist for an improved system for mounting dental casts to mounting plates on a dental articulator.